1. Field of the Invention
The present invention relates generally to integrated circuit (IC) chip and package technology and, more particularly, to chip pad arrangements for a driver IC chip in a liquid crystal display (LCD) and a related circuit pattern structure of a tape automated bonding (TAB) package.
2. Description of the Related Art
Since the 1960's, LCDs have been used in calculators and digital watches. In recent years, LCDs represent remarkable progress in monitors for notebook computers and desktop computers. LCD technology will be likely applied to many products in a variety of fields.
In general, an LCD module is composed of an LCD panel having a liquid crystal suspension between two transparent panels, a backlight illuminating the LCD panel from beneath, and a driver unit applied to the LCD panel.
FIG. 1 shows, in a plan view, a conventional LCD module. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1.
Referring to FIGS. 1 and 2, an LCD panel 10 has two glass substrates 11 and 12 and a liquid crystal layer 13 interposed between the glass substrates 11 and 12. On the glass substrates 11 and 12 are respectively provided thin film transistors (TFTs) and color filters. Subjecting the liquid crystal layer 13 to varying amounts of electrical charges, under the control the TFTs, crystals in the liquid crystal layer 13 change orientation to allow variation in the amount of light passing therethrough.
A driver unit 20, in the form of a TAB package, includes a base film 21 with circuit patterns 22 thereon. An IC chip 30 attaches to the circuit patterns 22 of the base film 21. The IC chip 30 is mechanically and electrically connected to the circuit patterns 22 through conductive bumps such as metal bumps 31 formed on input/output (I/O) pads of the IC chip 30. Most of the circuit patterns 22 are covered with a solder resist 23. Furthermore, a sealing resin 24, interposed between the IC chip 30 and the base film 21, protects the electrical connections. This type of TAB package 20 is known in the art as a chip-on-film (COF) package.
The TAB package 20 is connected to the TFTs of substrate 11 of the LCD panel 10 at a first peripheral region 25. In a typical LCD module, the TAB package 20 is further connected to a printed circuit board (PCB) at a second peripheral region 26. The PCB offers control signals and data signals necessary to driving the LCD panel 10. However, a recent advanced LCD module does not include the PCB, instead it transfers the functions of the PCB to both the IC chip 30 and the LCD panel 10. The above-discussed LCD module in FIGS. 1 and 2 is of the latter case, i.e., a TAB package without the PCB connections in the second peripheral region 26.
FIG. 3 shows, in a plan view, a pad arrangement of the IC chip 30 and the circuit patterns 22 of the TAB package 20 shown in FIGS. 1 and 2.
Referring to FIG. 3, because of the absence of the PCB connections in peripheral region 26, both the output patterns 22a and the input patterns 22b are routed to the first peripheral region 25. However, since the input patterns 22b must pass though the second peripheral region 26, the relatively narrower second peripheral region 26 accommodates only a limited number of the patterns 22.
The IC chip 30, used as the LCD driver, has in general a much greater number of output pads 32a than input pads 32b. 
If the second peripheral region 26 of the TAB package 20 increases in width, the output pads 32a may also be arranged along the upper longer side of the IC chip 30. However, the increase in width of the second peripheral region 26 may not only cause an unfavorable rise in production cost, but also lead to an increased size of the final LCD product. Accordingly, a new technique that arranges the output pads 32b to the upper longer side of the IC chip 30 without increasing the size of the TAB package 20 is desirable.